Duties and Reports of the Subsurface Geologist 853 



Acknowledgements 

 Stratigraphic summary 

 Hosston formation 

 Definition 



Distribution and thickness 

 Stratigraphic and lithologic features 

 Correlation 

 Sligo formation 



(treated as above) 

 References 

 Table 1. Correlation of Lower Cretaceous formations of the coastal plain of 



Arkansas, Louisiana, and Texas. 

 Table 2. Formation tops in Comanche and older rocks in south Texas and 



Mexico. 

 Table 3. Known range in thickness of the Cretaceous formation of pre-Gulf age 



in south Texas. 

 Figure 1. Index map of south Texas and northern Mexico showing the location 



of wells. 

 Figure 2. Columnar sections from central mineral region to Frio County, Texas 



(graphic and electric log). 

 Figure 3. Columnar section from Limestone County to Atascosa County, Texas 

 (graphic and electric log) . 



Report on a Petroliferous Province^^ 



I. Introduction. 



1. Importance today and in earlier history. 



2. Location and boundaries. Illustrate with map showing location of 

 productive areas and names of more important fields. Give states in- 

 volved and relative iraportance of each. 



3. Subprovinces if any. 



4. Date of discovery and history of development. Most active areas at 

 present. 



5. Unusual characteristics in the geology and in the occurrence of oil 

 and gas. 



6. Surface indications of oil and gas. 

 II. Geomorphology and general geology. 



General statement regarding physiography, range in age of rocks, 

 thickness of strata, regional and local structure and their influence on 

 topography, igneous activity, extent of exposures, explanation of tech- 

 niques best adapted to area. 



III. Stratigraphy. 



1. Thickness, character, age, and distribution of the rocks. 



2. Stratigraphic table or, preferably, columnar section or sections. 



3. Description of surface and subsurface formations by systems. Corre- 

 lation chart. 



4. Lateral variations in thickness and character (facies changes), sources 

 of sediments, shifting of axis of geosyncline of deposition, old shore 

 lines. 



5. Unconformities. Wedge areas. Overlap and offlap relations. Buried 

 topographic features, etc. 



6. Key horizons. 



7. Methods of subsurface correlation. 



8. Producing horizons, continuity, lithologic character. 



IV. Structure. 



1. Description of surface and subsurface regional structure and relation 

 to other major tectonic features. Rate of dip, etc. (Use structure con- 

 tour map or maps and cross sections) . Age and origin. 



2. Influence on distribution of formations. 



'° By F. M. Van Tuyl, department of geology, Colorado School of Mines. 



